1. Field of the Invention
This invention relates to devices for sensing ambient air conditions, and more particularly to an apparatus for sensing the various ambient conditions which effect human comfort so that the sensed conditions may be correlated to arrive at a comfort index, or effective temperature.
2. Description of the Prior Art
The ambient air conditions which determine the comfort of human beings includes the basic factors of air temperature, humidity, air movement and mean radiation. Each of these factors are mutually interrelated and have a direct bearing on the comfort of human beings.
It is well recognized that a person may experience varying degrees of comfort at a particular temperature. For example, at a given temperature, if the humidity is high, a greater degree of discomfort is felt as compared to the same temperature at a lower humidity. In addition to temperature, humidity and mean radiation, comfort is effected by movement of the surrounding air.
In U.S. Pat. No. 3,095,742, a direct reading comfort index thermometer is disclosed which includes a thermometer one-half of the bulb of which is covered by a moisture absorbing fabric in the form of a wick. The wick extends into a water reservoir and moisture is thus conducted, or wicked, to that portion of the wick which is in contact with the bulb of the thermometer. The uncovered portion of the bulb senses dry bulb temperature and the covered portion senses wet bulb temperature with the result that the thermometer will correlate those two sensed temperatures and produce a reading at a point about half way therebetween. This prior art device is relatively complex due to the structural arrangements of the wick and the reservoir, and the proximity of the water reservoir to the blub can cause distortion in the accuracy of the device. Further, this device makes no provisions for the effects of ambient air movements on the comfort of human beings.
In general, most comfort index devices are similar to the above described particular device in that they make no provisions for consideration of air movement and mean radiation, and are intended for use only during warm seasons of the year.
In U.S. Pat. No. 3,771,364, issued to me on Nov. 13, 1973, I disclosed a comfort index thermometer which overcomes some of the problems and shortcomings of prior art devices. In my patented structure, I employ a thermometer having its bulb partially covered with an absorbent material which is moistened when desired by opening a simple valve means that delivers water from a water reservoir, with the reservoir being disposed so as to be remote from the bulb. In this manner, the structure is exceptionally simple and no distortion of the sensed readings results from the proximity of the reservoir. Further, this structure is provided with a chart alongside the thermometer, which shows corrections that are to be made in the reading of the thermometer to allow for various air movement conditions. Thus, my patented device takes into account air temperature, humidity and air movement, the factors which effect human comfort. However, that device does not efficiently sense mean radiation, and no means for determining wind velocity is provided. Therefore, the user must rely either on guess work or on obtaining of wind speed data from other sources. The disadvantage of employing guess work is obvious, and since air movements will vary from place to place, data obtained such as from radio weather reports and the like is unreliable. Thus, a user desiring accurate, or fairly accurate, comfort index readings has no choice but to purchase a separate wind speed sensing instrument.
Therefore, a need exists for a new and improved comfort factor apparatus which overcomes some of the problems and shortcomings of the prior art.